Analytical analysis
Independent samples T-test used for comparing the frequency of different
factors between unipolar non-steroid-eluting and bipolar steroid-eluting
leads. Logistic regression was used in the case of categorical variables
with more than two categories. Survival analysis was done on a subgroup
of patients, that their lead failure was due to the primary failure
reasons (unacceptable high pacing threshold and sensing abnormality,
lead fracture, loss of capture, and lead displacement). The
characteristics of these patients were also calculated and presented
with the abovementioned descriptive analysis. For a 48-month follow-up
time, Kaplan Meier analysis and Weibull regression hazards model was
used for survival analysis of all variables.9Accordingly, hazard ratio was estimated for each variable with a 95%
confidence interval (95%CI). Afterward, age and lead type (bipolar
steroid-eluting and unipolar non-steroid eluting) adjusted hazard ratio
calculated for variables using Weibull regression hazards model. The
level of significance was considered as p<0.05 throughout the
study.